feat: let admins turn off the custom From address in the composer

app/(main)/admin/_tabs/policy.tsx

@@ -39,6 +39,7 @@ const FEATURE_GATE_LABELS: Partial<Record<keyof FeatureGates, { label: string; d
   crossAllViewEnabled: { label: 'Unified Mailbox: All Mail', description: 'Allow an "All mail" entry in the Unified Mailbox section that lists all mail across the account and its shared folders (or every account when the cross-account sub-option is on). Honors the user\'s folder selection. Requires the matching per-user toggle in Settings → Appearance.' },
   unifiedCrossAccountEnabled: { label: 'Unified Mailbox: Cross-account', description: 'Allow users to expand the Unified Mailbox beyond the active account boundary so its lists merge across every logged-in account. When off, the Unified Mailbox stays within the active account and its shared folders.' },
   accountArchiveEnabled: { label: 'Account List Backup', description: 'Let users save their list of accounts (address, server, label, colour) on this server, encrypted in the browser with a password of their choice, and restore it on another device. No mailbox passwords are stored. Archives live in SETTINGS_DATA_DIR/account-archives; requires SESSION_SECRET.' },
+  customFromEnabled: { label: 'Custom From Address', description: 'Let users type any sender address in the composer instead of picking one of their identities, and let replies to a catch-all address on their domain send from that address. Turn this off when users may only send as their configured identities.' },
 };
 
 const RESTRICTABLE_SETTINGS = [

components/email/__tests__/composer-from-override-envelope.test.tsx

@@ -1,7 +1,8 @@
 import { render, screen, fireEvent, waitFor } from '@testing-library/react';
-import { describe, it, expect, vi, afterEach } from 'vitest';
+import { describe, it, expect, vi, beforeEach, afterEach } from 'vitest';
 import React from 'react';
 import { EmailComposer } from '../email-composer';
+import { usePolicyStore } from '@/stores/policy-store';
 
 // ─── Heavy component mocks (mirrors composer-reopened-draft-signature.test.tsx) ─
 
@@ -247,4 +248,35 @@ describe('composer From override envelope (#1009)', () => {
     expect(sent.fromEmail).toBe('me@example.com');
     expect(sent.envelopeMailFrom).toBeUndefined();
   });
+
+  describe('with custom From switched off by the admin', () => {
+    const setCustomFrom = (on: boolean) => usePolicyStore.setState((state) => ({
+      policy: { ...state.policy, features: { ...state.policy.features, customFromEnabled: on } },
+    }));
+    beforeEach(() => setCustomFrom(false));
+    afterEach(() => setCustomFrom(true));
+
+    it('sends a draft saved with a custom From from its identity', async () => {
+      const onSend = vi.fn();
+      render(<EmailComposer initialData={{ ...DRAFT, fromOverrideEmail: 'shop@example.com' }} onSend={onSend} />);
+      expect(screen.queryByDisplayValue('shop@example.com')).not.toBeInTheDocument();
+
+      const sent = await send(onSend);
+      expect(sent.fromEmail).toBe('me@example.com');
+      expect(sent.envelopeMailFrom).toBeUndefined();
+    });
+
+    it('offers no Custom button', () => {
+      render(<EmailComposer />);
+      expect(screen.queryByText('from_override.toggle_off')).not.toBeInTheDocument();
+    });
+
+    // Control: the button is there with the gate on, so the test above is not
+    // passing on a renamed label.
+    it('offers the Custom button with the gate on', () => {
+      setCustomFrom(true);
+      render(<EmailComposer />);
+      expect(screen.getByText('from_override.toggle_off')).toBeInTheDocument();
+    });
+  });
 });

components/email/__tests__/reply-addressing.test.tsx

@@ -5,6 +5,7 @@ import { EmailComposer } from '../email-composer';
 import { useSettingsStore } from '@/stores/settings-store';
 import { useAuthStore } from '@/stores/auth-store';
 import { useAccountStore } from '@/stores/account-store';
+import { usePolicyStore } from '@/stores/policy-store';
 
 // ─── Heavy component mocks (mirrors recipient-paste.test.tsx) ─────────────────
 
@@ -357,6 +358,24 @@ describe('composer reply addressing', () => {
     }
   });
 
+  // The admin's custom From gate takes the rewrite away even when the user
+  // asked for domain matching.
+  it('does not rewrite From when the admin turned custom From off', () => {
+    const setCustomFrom = (on: boolean) => usePolicyStore.setState((state) => ({
+      policy: { ...state.policy, features: { ...state.policy.features, customFromEnabled: on } },
+    }));
+    setAutoSelect(true);
+    setCustomFrom(false);
+    try {
+      render(<EmailComposer mode="reply" replyTo={RECEIVED_CATCH_ALL} />);
+      expect(screen.queryByDisplayValue('colleague@example.com')).toBeNull();
+      expect(identitySelect().value).toBe('id-me');
+    } finally {
+      setAutoSelect(false);
+      setCustomFrom(true);
+    }
+  });
+
   it('never rewrites From on a forward, even with the setting on', () => {
     setAutoSelect(true);
     try {

components/email/email-composer.tsx

@@ -483,6 +483,7 @@ export function EmailComposer({
   const { isFeatureEnabled } = usePolicyStore();
   const templatesEnabled = isFeatureEnabled('templatesEnabled');
   const filesEnabled = isFeatureEnabled('filesEnabled');
+  const customFromEnabled = isFeatureEnabled('customFromEnabled');
 
   // The signature identity used when embedding the signature into the initial
   // body for "above quote" mode. Mirrors the signatureIdentity derivation
@@ -799,7 +800,10 @@ export function EmailComposer({
   // signature, also when it has none (see ownSignatureIdentity).
   const [identityPickedByUser, setIdentityPickedByUser] = useState(false);
   const [subAddressTag, setSubAddressTag] = useState<string>(initialData?.subAddressTag ?? '');
-  const [fromOverrideEnabled, setFromOverrideEnabled] = useState<boolean>(initialData?.fromOverrideEnabled ?? false);
+  const [fromOverrideChosen, setFromOverrideEnabled] = useState<boolean>(initialData?.fromOverrideEnabled ?? false);
+  // With the admin's customFromEnabled gate off, a draft saved with a custom
+  // From opens, sends and saves again from its identity instead.
+  const fromOverrideEnabled = customFromEnabled && fromOverrideChosen;
   const [fromOverrideEmail, setFromOverrideEmail] = useState<string>(initialData?.fromOverrideEmail ?? '');
   const [fromOverrideName, setFromOverrideName] = useState<string>(initialData?.fromOverrideName ?? '');
   const [showTemplatePicker, setShowTemplatePicker] = useState(false);
@@ -1108,7 +1112,9 @@ export function EmailComposer({
     // lets a user keep the setting on but limit it to configured identities,
     // for domains where the other addresses are distribution lists (#1000).
     if (autoSelectReplyIdentity && mode !== 'forward') {
-      const resolved = resolveReplyFrom(sourceAccountIdentities, recipients, replyIdentityMatch);
+      // Without custom From the catch-all rewrite has nothing to write into.
+      const matchMode = customFromEnabled ? replyIdentityMatch : 'exact';
+      const resolved = resolveReplyFrom(sourceAccountIdentities, recipients, matchMode);
       if (resolved) {
         setSelectedIdentityId(resolved.identityId);
         if (resolved.overrideEmail && !fromOverrideEnabled) {
@@ -1134,6 +1140,7 @@ export function EmailComposer({
   }, [
     autoSelectReplyIdentity,
     replyIdentityMatch,
+    customFromEnabled,
     composeFromAccountEmail,
     fromOverrideEnabled,
     identities,
@@ -3620,28 +3627,30 @@ export function EmailComposer({
                   <X className="w-3 h-3" />
                 </Button>
               )}
-              <Button
-                type="button"
-                variant={fromOverrideEnabled ? 'outline' : 'ghost'}
-                size="sm"
-                onClick={() => {
-                  if (fromOverrideEnabled) {
-                    setFromOverrideEnabled(false);
-                  } else {
-                    setFromOverrideEnabled(true);
-                    if (!fromOverrideEmail && currentIdentity?.email) {
-                      setFromOverrideEmail(currentIdentity.email);
+              {customFromEnabled && (
+                <Button
+                  type="button"
+                  variant={fromOverrideEnabled ? 'outline' : 'ghost'}
+                  size="sm"
+                  onClick={() => {
+                    if (fromOverrideEnabled) {
+                      setFromOverrideEnabled(false);
+                    } else {
+                      setFromOverrideEnabled(true);
+                      if (!fromOverrideEmail && currentIdentity?.email) {
+                        setFromOverrideEmail(currentIdentity.email);
+                      }
+                      if (!fromOverrideName && currentIdentity?.name) {
+                        setFromOverrideName(currentIdentity.name);
+                      }
                     }
-                    if (!fromOverrideName && currentIdentity?.name) {
-                      setFromOverrideName(currentIdentity.name);
-                    }
-                  }
-                }}
-                className="h-6 px-2 text-xs shrink-0"
-                title={t('from_override.toggle_tooltip')}
-              >
-                {fromOverrideEnabled ? t('from_override.toggle_on') : t('from_override.toggle_off')}
-              </Button>
+                  }}
+                  className="h-6 px-2 text-xs shrink-0"
+                  title={t('from_override.toggle_tooltip')}
+                >
+                  {fromOverrideEnabled ? t('from_override.toggle_on') : t('from_override.toggle_off')}
+                </Button>
+              )}
             </div>
           </div>
           {overrideEnvelopeFallback && (

components/settings/composing-settings.tsx

@@ -5,6 +5,7 @@ import { useTranslations } from 'next-intl';
 import { useSettingsStore } from '@/stores/settings-store';
 import type { ReplyIdentityMatch, SendDelaySeconds } from '@/stores/settings-store';
 import { useAuthStore } from '@/stores/auth-store';
+import { usePolicyStore } from '@/stores/policy-store';
 import { SettingsSection, SettingItem, Select, ToggleSwitch } from './settings-section';
 import { X } from '@/components/icons';
 import {
@@ -39,6 +40,8 @@ export function ComposingSettings() {
   } = useSettingsStore();
   const { client } = useAuthStore();
   const delayedSendSupported = client?.hasDelayedSend() ?? false;
+  // Catch-all matching only rewrites From, which the admin can switch off.
+  const customFromEnabled = usePolicyStore((s) => s.isFeatureEnabled('customFromEnabled'));
 
   return (
     <SettingsSection title={t('title')} description={t('description')}>
@@ -49,7 +52,7 @@ export function ComposingSettings() {
         />
       </SettingItem>
 
-      {autoSelectReplyIdentity && (
+      {autoSelectReplyIdentity && customFromEnabled && (
         <SettingItem label={t('reply_identity_match.label')} description={t('reply_identity_match.description')}>
           <Select
             value={replyIdentityMatch}

lib/admin/types.ts

@@ -63,6 +63,8 @@ export interface FeatureGates {
   unifiedCrossAccountEnabled: boolean;
   /** Encrypted account list kept on the server, restorable on another device. */
   accountArchiveEnabled: boolean;
+  /** Composer "Custom" From: free-text sender address instead of an identity. */
+  customFromEnabled: boolean;
 }
 
 export const DEFAULT_FEATURE_GATES: FeatureGates = {
@@ -91,6 +93,7 @@ export const DEFAULT_FEATURE_GATES: FeatureGates = {
   crossAllViewEnabled: false,
   unifiedCrossAccountEnabled: false,
   accountArchiveEnabled: false,
+  customFromEnabled: true,
 };
 
 export interface ThemePolicy {